三相電加熱管

        380伏(fu)(fu)三(san)(san)相四(si)線電(dian)(dian)路中(zhong)，任意兩根火線之間(jian)的電(dian)(dian)壓都是380伏(fu)(fu)，任意一根火線與零(ling)線之間(jian)都可以組成220伏(fu)(fu)。這個(ge)系統可以形成三(san)(san)種(zhong)電(dian)(dian)源(yuan)(yuan)：即單(dan)相220伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)，單(dan)相380伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)，三(san)(san)相380伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)，第 I 種(zhong)家用(yong)(yong)比(bi)較多，第三(san)(san)種(zhong)工廠里電(dian)(dian)機類用(yong)(yong)得多，第二種(zhong)用(yong)(yong)得少，只有交流電(dian)(dian)焊機經常用(yong)(yong)到(dao)單(dan)相380伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)。